biotin-avidin binding

Nonspecific binding could be a problem. Try the new
NeutrAvidin-HRP conjugate from Pierce (prod 31001).
NeutrAvidin is simply de-glycosylated avidin, and has
inherently lower non-specific binding, mainly due to the
neutral isoelectric point.
On the other hand, you might be seeing endogenously
biotinylated proteins!!! In which case you CAN NOT
use avidin-HRP since you would pick up those bands.
Keld .